This invention relates to the manufacturing of polyester fabric for wipers, in particular, wipers which release fewer particulate contaminates.
Wipers may be made from knitted, woven or non-woven polyester fabrics. The typical manufacturing process begins with drawing and texturing continuous filament polyester yarn. The textured yarn is knitted or woven to construct a fabric, and the fabric is washed or scoured to remove spinning oils. The fabric may be chemically modified in order to improve its wettability and performance. The fabric is then dried in a xe2x80x9ctenter framexe2x80x9d oven at a temperature of between 325 and 450xc2x0 F., to remove moisture and heat set the fabric. Heat setting dissipates stress in the polyester fibers and stabilizes the fabric.
Next, the fabric is cut into wipers, typically 9 inch by 9 inch squares. The wipers may remain unlaundered or may be washed in a cleanroom laundry, employing special surfactants and highly-filtered and purified water, to reduce the contamination present on the fabric. After washing, the wipers may be packaged dry in air-tight plastic bags, or pre-saturated with a suitable solvent before being packaged, and are ready for use.
These wipers are utilized for a number of different applications, including cleaning within cleanrooms, automotive painting rooms and other cleanroom environments. Each different application emphasizes certain standards these types of wipers should attain. For example, for wipers utilized in cleanrooms, stringent performance standards must be met. These standards are related to sorbency and contamination, including maximum allowable particulate, unspecified extractable matter and individual ionic contaminants. The standards for particulate contaminant release are especially rigorous and various methods have been devised to meet them. For example, Paley et al., U.S. Pat. No. 4,888,229, describes a wiper having fused borders, the sealed edge of the wipers being present to reduce contamination caused by small fibers. Diaber et al., U.S. Pat. No. 5,229,181, describes a knit fabric tube, only two edges of which must be cut and sealed, thereby reducing the contamination caused by loose fibers from the edges. Paley et al., U.S. Pat. No. 5,271,995, describes a wiper for a cleanroom environment that has reduced inorganic contaminants through the use of a specific yarn, namely xe2x80x9cnylon brightxe2x80x9d. Reynolds, U.S. Pat. No. 5,069,735, describes a procedure to cut the fabric into pieces using a hot air jet in the range of 600 to 800xc2x0 F. to melt the fibers, forming a sealed edge product with reduced loose fiber contamination.
Despite advances made in reducing particulate contamination release from cleanroom wipers, further reductions in particulate release are, nevertheless, highly desirable.
Therefore, an object of the invention is to provide a low contaminant wiping cloth suitable for a wide range of applications. Another object of the invention is to provide a wiper which meets substantially all of the specifications for use in cleanrooms, particularly Class 100 cleanrooms and below, to provide an improved method of manufacturing a cleanroom wiper and to provide a wiper having a substantial reduction in particulate release. A further object of the invention is to provide a cleanroom wiper having a high liquid sorbency capacity. Yet another object of the invention is to provide a wiper which is dimensionally stable. The term dimensionally stable means, in this instance, a wiper which lies substantially flat and does not curl into a roll, especially after the wiper is laundered. Preferably, the wiper does not undergo any appreciable linear shrinkage (less than 5%) when it is exposed to a heat source of 175 degrees fahrenheit for 5 minutes.
Accordingly, a method of manufacturing a textile article for use in a cleanroom is provided having the steps of constructing a knitted or woven fabric from polyester yarn, heat setting the fabric at a temperature of from 1 80xc2x0 to 300xc2x0 F. and cutting the fabric to form the desired article; wherein the polyester fiber has not been heated above a temperature of 300xc2x0 F. The invention also includes a textile article, such as a wiper, made according to the aforementioned process.
Without being bound to a particular theory, it is believed that heating the polyester fiber above 300xc2x0 F. causes low molecular weight polymers or oligomers to blossom to the surface of the polyester fiber, where they crystalize into small particles. These small particles, known as xe2x80x9ctrimer particlesxe2x80x9d can number as high as 1xc3x97109 or greater particles per square meter, have a high affinity for the polyester fabric and are very difficult to remove using conventional laundering procedures. Nevertheless, the trimer particles can release from the fabric and become a source of contamination. Applicant has established a direct correlation between the temperature to which the polyester fiber has been exposed and particulate contamination released from the fabric.
The invention, including alternate embodiments thereof, incorporates the advantages of being adaptable to existing manufacturing processes; reducing particulate contamination on the fiber dramatically; being useful with conventional polyester fibers: and having high sorbency capacity and dimensional stability, as defined above.